For a woman who has just won the £30,000 Orange prize for fiction, Chimamanda Ngozi Adichie is rather downbeat. “Did I expect to win?” she says. “No. I’m never lucky at these things. I had been told endlessly that I was the favourite and I’m a bit superstitious. I didn’t think favourites ever won. And then the night before, my bag got stolen during a reading. I didn’t even want to turn up. I wasn’t in a good place, I felt violated and awful.”

Worrying about her stolen personal effects did take her mind off being nervous. “When the presenter was up on stage, talking about Orange, I was thinking about my stolen Sim card and changing my air ticket. So in a way it calmed me down. And when my name was called, I thought: oh. My boyfriend had to urge me to go up to the stage.”

Adichie may have been surprised, but her winning novel Half of a Yellow Sun (HarperPerennial, £7.99), an ambitious, multi-narrated epic set amid the chaos of the Nigerian-Biafran war of the late 1960s (both her grandfathers died in it and the novel is dedicated to them), has already been hailed as a classic and Adichie, still only 29, as an important voice in literary fiction.

Not “African” literary fiction, mind: Adichie is wary about labels and indignant about the “ethnic” tag which so often gets attached to nonwestern writers. “I accept labels a bit more now, but there are expectations which come with them. Nigerian writers are supposed to write a certain way.”

Multimedia

• Pictures: Orange Broadband Prize for Fiction 2007

The consolations of civil war

Helen Dunmore reviews Half of a Yellow Sun by Chimamanda Ngozi Adichie

• Half of a Yellow Sun by Chimamanda Ngozi Adichie

A nation's memory

Half of a Yellow Sun by Chimamanda Ngozi Adichie

Background

• Review: Fiction: Purple Hisbiscus by Chimamanda Ngozi Adichie

• Hugo Barnacle reviews Half of a Yellow Sun

They are certainly not meant to write about middle-class Africans, which she does, about life in academia (her parents are both academics and she grew up in the university town of Nsukka), which she does, about sex and relationships and essentially the stuff of the “mainstream” novel. “I just hope people come away from my books with a sense that Africans are human,” she says. “American readers, in particular, have often told me how surprised they were that the characters were just like them. And that I write in English.”

Would she ever consider writing in anything other than English? The question irks her: “Every time I do an event outside Nigeria, the question invariably arises. I grew up speaking both English and Igbo and learnt both at the same time. But to be an ‘authentic’ African it seems that you must write in an African language.”

Fair enough, yet Adichie’s determined internationalism is somewhat hazy around the edges. Take her choice of dress for the Orange prize. “I wanted to look Nigerian, but I didn’t have anything, so I had to be creative and make something Nigerian,” she explains, proudly showing me a photograph of herself looking radiant in a white strapless affair, a printed fabric turban on her head. Isn’t that a bit like writing a book in Nigerian dialect? “No, not at all,” she says.

Indeed, although she has studied and worked in the United States for the past 10 years, Adichie calls Nigeria her home and is adamant that she will never swap her Nigerian passport for anything else.

“There is something authentically Nigerian about being humiliated in foreign embassies when you want to get a visa,” she explains wryly. “The only embassy which has ever been polite to me was the Canadian embassy. Do you want to hear about the British embassy in Lagos? Horribly rude. I will never forget this old man ahead of me in line once. He must have been in his seventies, spoke bad English, and this official was shouting at him, ‘You are a liar, you’re a liar. Security, get him out of here’. And I thought: you don’t have to do this. At least leave him with his dignity.”

Perhaps because she is young, beautiful and internationally successful, Adichie has almost a paradoxical relish in hailing from a global underdog: “When you come from Nigeria, which doesn’t have very much power, you can better examine the dynamics of raw power.”

Something she does not relish, however, is the overriding view of Africa as a doomed basket case: “There is a famous saying, ‘Africa is my brother, but he is my junior brother’, which comes from a 19th-century missionary in the Congo. It really sums up the way that people look at Africa today.”

Madonna’s public fervour about African orphans, for example, makes Adichie’s eyes roll: “Madonna is free to adopt children from wherever she wants. But I heard her saying that she wanted people to go to Africa and adopt children. Nobody helps Africa by adopting its children. We need to talk about structural things like loans and trade. I just wish I wasn’t from a continent about which everyone has to feel sorry.”

Adichie is indignant about the type of news coverage that Africa usually ends up with: “On TV you never see Africans involved in helping Africa. It’s always some kind westerner. If I got my information only from American TV, I would think Africans were a bunch of stupid idiots.”

Equally, the Bob Geldof modus operandi does not do much for Adichie: “The Africa that you see on TV here is not the Africa I know. Africans don’t sit down, filled with despair, at least the ones I know don’t. They move on with life. Even in the poorest areas of Africa there are people who are showing initiative. There are other stories to tell.”

What about the legendary African political corruption? Human nature, says Adichie: “If you put anyone into a system where they would get away with massive corruption, they would do it.”

Really? “Yes. I think there is a tendency in human beings where if there is nobody checking up on you and you can call up the central bank and ask for, say, $5m to be diverted into your account, you will do it.”

Would she do it? “No,” she says instantly. “I would not.” Why? Are novelists incorruptible? To her credit, she laughs at this: “No. I would never steal, but then I have never been put in a place where I might need to . . . I know good and kind people who have taken up positions of power in Nigeria and have just become . . .” she shrugs. “America is a place of checks and balances. So when Bush gives his friends contracts in Iraq, there is only so much he can do. If you put Bush into a Nigerian context, he would also be giving his friends oilfields, because our system just doesn’t have checks and balances. We don’t have an independent judiciary. Or a strong civil society. We don’t even have a real democracy.”

Nigeria may not have checks and balances, but in her view it seems to be the Americans who are the idiots, worshipping a celebrity culture that she despises and a body culture she rejects. “The west African ideal of beauty is that a woman should have flesh and curves. In Nigeria being thin is not a good thing because it suggests that one cannot afford to eat. But in America when you tell someone they are thin, people say, ‘Oh, thank you’. For me that was a shock. Also to learn that ‘fat’ is a bad word. In Nigeria it’s just an adjective. In America food is not something you enjoy. When I go home to Nigeria I realise how ridiculous it all is. I like food and I will not apologise for liking it.”

So why has Adichie been in America for the past decade? “Because America has money. That’s why.” She shrugs. “They pay you to study. It’s the reason why America has the best scholars, the best universities and the best archives. It is why Yale [where she is doing a masters in African studies] has a fantastic library and why I can find books I will never find anywhere else.”

It is also the only global super-power and I rather get the feeling that Adichie enjoys being near the heart of the action. “I would love to be part of the G8,” she says. “To be one of those eight people sitting around the table, determining the fate of a continent. It must be heady.”

Until she gets the call from the White House, what next? “I’m hoping to settle down to my next novel. It’s about Nigerian emigrants, and if that horrible person at the Purcell Room hadn’t stolen my bag, which contained my notebook full of jottings and ideas . . . but anyway. I am going to go home and wait for the literary spirits to call me.”

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